// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_BASE_IME_INPUT_METHOD_H_
#define UI_BASE_IME_INPUT_METHOD_H_

#include <stdint.h>

#include <string>

#include "base/event_types.h"
#include "build/build_config.h"
#include "ui/base/ime/text_input_mode.h"
#include "ui/base/ime/text_input_type.h"

namespace ui {

namespace internal {
    class InputMethodDelegate;
} // namespace internal

class InputMethodObserver;
class KeyEvent;
class TextInputClient;

// An interface implemented by an object that encapsulates a native input method
// service provided by the underlying operating system, and acts as a "system
// wide" input method for all Chrome windows. A class that implements this
// interface should behave as follows:
// - Receives a keyboard event directly from a message dispatcher for the
//   system through the InputMethod::DispatchKeyEvent API, and forwards it to
//   an underlying input method for the OS.
// - The input method should handle the key event either of the following ways:
//   1) Send the original key down event to the focused window, which is e.g.
//      a NativeWidgetAura (NWA) or a RenderWidgetHostViewAura (RWHVA), using
//      internal::InputMethodDelegate::DispatchKeyEventPostIME API, then send
//      a Char event using TextInputClient::InsertChar API to a text input
//      client, which is, again, e.g. NWA or RWHVA, and then send the original
//      key up event to the same window.
//   2) Send VKEY_PROCESSKEY event to the window using the DispatchKeyEvent API,
//      then update IME status (e.g. composition text) using TextInputClient,
//      and then send the original key up event to the window.
// - Keeps track of the focused TextInputClient to see which client can call
//   APIs, OnTextInputTypeChanged, OnCaretBoundsChanged, and CancelComposition,
//   that change the state of the input method.
// In Aura environment, aura::WindowTreeHost creates an instance of
// ui::InputMethod and owns it.
class InputMethod {
public:
#if defined(OS_WIN)
    typedef LRESULT NativeEventResult;
#else
    typedef int32_t NativeEventResult;
#endif

    virtual ~InputMethod()
    {
    }

    // Sets the delegate used by this InputMethod instance. It should only be
    // called by an object which manages the whole UI.
    virtual void SetDelegate(internal::InputMethodDelegate* delegate) = 0;

    // Called when the top-level system window gets keyboard focus.
    virtual void OnFocus() = 0;

    // Called when the top-level system window loses keyboard focus.
    virtual void OnBlur() = 0;

    // Called when the focused window receives native IME messages that are not
    // translated into other predefined event callbacks. Currently this method is
    // used only for IME functionalities specific to Windows.
    // TODO(ime): Break down these messages into platform-neutral methods.
    virtual bool OnUntranslatedIMEMessage(const base::NativeEvent& event,
        NativeEventResult* result)
        = 0;

    // Sets the text input client which receives text input events such as
    // SetCompositionText(). |client| can be NULL. A gfx::NativeWindow which
    // implementes TextInputClient interface, e.g. NWA and RWHVA, should register
    // itself by calling the method when it is focused, and unregister itself by
    // calling the method with NULL when it is unfocused.
    virtual void SetFocusedTextInputClient(TextInputClient* client) = 0;

    // Detaches and forgets the |client| regardless of whether it has the focus or
    // not.  This method is meant to be called when the |client| is going to be
    // destroyed.
    virtual void DetachTextInputClient(TextInputClient* client) = 0;

    // Gets the current text input client. Returns NULL when no client is set.
    virtual TextInputClient* GetTextInputClient() const = 0;

    // Dispatches a key event to the input method. The key event will be
    // dispatched back to the caller via
    // ui::InputMethodDelegate::DispatchKeyEventPostIME(), once it's processed by
    // the input method. It should only be called by a message dispatcher.
    virtual void DispatchKeyEvent(ui::KeyEvent* event) = 0;

    // Called by the focused client whenever its text input type is changed.
    // Before calling this method, the focused client must confirm or clear
    // existing composition text and call InputMethod::CancelComposition() when
    // necessary. Otherwise unexpected behavior may happen. This method has no
    // effect if the client is not the focused client.
    virtual void OnTextInputTypeChanged(const TextInputClient* client) = 0;

    // Called by the focused client whenever its caret bounds is changed.
    // This method has no effect if the client is not the focused client.
    virtual void OnCaretBoundsChanged(const TextInputClient* client) = 0;

    // Called by the focused client to ask the input method cancel the ongoing
    // composition session. This method has no effect if the client is not the
    // focused client.
    virtual void CancelComposition(const TextInputClient* client) = 0;

    // Called by the focused client whenever its input locale is changed.
    // This method is currently used only on Windows.
    // This method does not take a parameter of TextInputClient for historical
    // reasons.
    // TODO(ime): Consider to take a parameter of TextInputClient.
    virtual void OnInputLocaleChanged() = 0;

    // Returns the locale of current keyboard layout or input method, as a BCP-47
    // tag, or an empty string if the input method cannot provide it.
    virtual std::string GetInputLocale() = 0;

    // TODO(yoichio): Following 3 methods(GetTextInputType, GetTextInputMode and
    // CanComposeInline) calls client's same method and returns its value. It is
    // not InputMethod itself's infomation. So rename these to
    // GetClientTextInputType and so on.
    // Gets the text input type of the focused text input client. Returns
    // ui::TEXT_INPUT_TYPE_NONE if there is no focused client.
    virtual TextInputType GetTextInputType() const = 0;

    // Gets the text input mode of the focused text input client. Returns
    // ui::TEXT_INPUT_TYPE_DEFAULT if there is no focused client.
    virtual TextInputMode GetTextInputMode() const = 0;

    // Gets the text input flags of the focused text input client. Returns
    // 0 if there is no focused client.
    virtual int GetTextInputFlags() const = 0;

    // Checks if the focused text input client supports inline composition.
    virtual bool CanComposeInline() const = 0;

    // Returns true if we know for sure that a candidate window (or IME suggest,
    // etc.) is open.  Returns false if no popup window is open or the detection
    // of IME popups is not supported.
    virtual bool IsCandidatePopupOpen() const = 0;

    // Displays an on screen keyboard if enabled.
    virtual void ShowImeIfNeeded() = 0;

    // Management of the observer list.
    virtual void AddObserver(InputMethodObserver* observer) = 0;
    virtual void RemoveObserver(InputMethodObserver* observer) = 0;
};

} // namespace ui

#endif // UI_BASE_IME_INPUT_METHOD_H_
